A micro-channel device has been used to carry a small volume of a sample for processing and/or analysis. Processing of the sample has required thermocycling the sample through a plurality of different predetermined temperatures. By way of example, DNA sequencing has included replication of extracted and purified DNA fragments from a sample through a process called polymerase chain reaction (PCR), which requires rapid and precise thermocycling of the sample through three different temperatures. Temperature non-uniformity across the sample, at any of the predetermined temperatures, of more than one degree may inhibit suitable replication.
A thermoelectric cooler (TEC), or Peltier device, generally is a thermoelectric heat pump, which transfers heat from one side of the device to the other side of the device, and has been used in connection with DNA sequencing for thermocycling samples. In use, the device is placed in thermal communication with a DNA sample, and an appropriate voltage is applied across the device to create a temperature gradient for transferring heat between the sides of the device, either away from the sample to cool the sample or towards the sample to heat the sample. The polarity of the applied voltage determines whether the device heats or cools the sample.
Unfortunately, with a TEC device, heat may be lost (e.g., via convection and/or otherwise) to a greater degree at peripheral regions of the TEC device, relative to inner more central regions of the TEC device. Sources that may contribute to such heat loss include, but are not limited to, the ambient environment, a heat sink in thermal communication with the TEC device, and the device carrying the sample being thermocylced. This heat loss may lead to a dome-shaped temperature distribution or other temperature gradient across the surface of the TEC device and, hence, a dome-shaped temperature distribution across the sample. Moreover, over time, “hot” spots may form in peripheral regions of the TEC device, for example, due to induced thermal stress, leading to thermal drift, or a shift in the distribution of temperature across the TEC device.
Various approaches have been used in an attempt to improve temperature uniformity delivered by TEC devices. For example, a high conductivity heat spreader layer has been used in connection with TEC devices to reduce any temperature gradient. In yet another example, a thick, high thermal conductivity source plate has been used in connection with TEC devices to promote temperature uniformity. Unfortunately, these approaches pose other complications and/or additional costs.